How-To #1 Assemble a DC-Motor Robot Chassis | 221

HTHOW-TOsHow-To #1: Assemble DC-Motor Robot Chassis

Background:A chassis is the frame of a device. The components are attached to this frame. The chassis described in this How-To is for two geared DC motors with wheels, an Arduino™ with a motor controller shield, a battery pack, an H-bridge circuit board, and a rear wheel.

This chassis is made from wood, although other materials will certainly serve. The wood is pre-cut into five pieces: the front panel, the rear panel, two side panels, and a deck. Modeling glue for wood is the recommended adhesive. For precisely rectangular construction a corner clamp is high-ly recommended, although it is not absolutely required.

Materials:Included in Robot Body kit (part RB103)All the parts necessary to assemble the chassis and attach it to the Arduino,™ its navigation shield, the battery pack, and the DC motors are included in the kit.

Quan-tity Part Image Notes Catalog

Number

1 DeckThe top flat surface of the robot. The armadillo logo should be visible when the chassis is complete.

RB103

1 Front Panel

Curved along the bottom. Attaches on each side to the end of the side panel with the large rectangular cut-out.

2 Side Pan-els

End with large rectangular cutout should be near the front panel.

1 Rear PanelU-shaped opening, should be at-tached with the U opening down-ward.

1 Rear Wheel One-inch diameter wood ball with a hole through the center.

1 Rear Wheel Axel 3-inch dowel.

222 | Learn to Program in ArduinoTM C: 18 Lessons, from setup() to robots

Quan-tity Part Image Notes Catalog

Number

4 Nylon Spacers

4-40 threaded for mounting Arduino™ Uno.

RB103

8Nylon Pan Head Screws

For attaching the Arduino™ Uno to the nylon spacers, and the spacers to the robot deck.

8

Stainless 4-40 Pan Head Screws

For attaching DC motors to the side panels.

8Stainless 4-40 Hex Nuts

For attaching DC motors to the side panels.

Not included in kit:

Quan-tity Part Image Notes Catalog

Number

1 Arduino™ Uno

Single-board computer. This board is delicate and should be handled with care. When you are not using it, keep it in a box or plastic bag.

3102

1Motor

Controller Shield

May be assembled from parts or pur-chased as a kit. Find How-To instruc-tions can be found on http://www.LearnCSE.com.

MC101

2 DCMotors Geared DC motors, 6 volts. 3132

1

Battery Holder with

2.1mm connector. Holds 6 AA

cells.

May be assembled from kit or by following instructions on LearnCSE.com.

3131

4 AA cells Alkaline or rechargeable. 3118

How-To #1 Assemble a DC-Motor Robot Chassis | 223

HTQuan-tity Part Image Notes Catalog

Number

2

Wheels to match the geared DC motors

Rubber-tired wheel to fit DC motors. 3133

1 H-bridgeMay be assembled from parts or pur-chased as a kit. Instructions are in How-To #7 on LearnCSE.com.

1307

Tools:In addition to the parts, the following tools aid in the assembly of the robot chassis:

Quan-tity

Tool Image Notes

Small tube

Modeling glue for wood

Most wood glues will work, but Testors Cement for Wood Models sets quickly and is sufficiently strong. It is available from most hobby stores.

1Corner clamp

(optional)

This device is an easy way to ensure 90- de-gree corners for the chassis. It is inexpensive and available from Home Depot and most other tools suppliers. The one shown here, purchased from Home Depot, sells for approximately $9.

1 Screw driver Phillips-head, suitable for the pan head screws.

224 | Learn to Program in ArduinoTM C: 18 Lessons, from setup() to robots

Procedure:Follow the instructions for the type of glue. Drying and curing times are different. "Dry" often means the glued object does not need continued support. But the glue hasn't reached its full strength until it is "cured," that is, when the chemical reactions are complete. Curing usually re-quires several hours.

1. Glue the front and rear panels to the side panels as shown in Figure HT1-1.

Figure HT1-1. Front, rear, and side panels of robot chassis

Important

In Figure HT1-1 the panels are all upside down. It's important to ensure that:• the assembly lies perfectly flat when put together as shown.• the rectangle cutouts on the side panels are toward the front panel.• each of the corners is as close to a perfect 90-degree angle as possible.• the rounded corners of the side panels meet the rounded side of the front panel.

2. After the glue has dried and cured, turn the assembly over.

3. Glue the deck to the top.

Important

The location of the Armadillo image is critical. It must be on top and at the op-posite end of the curved front panel. See Figure HT1-2.

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HT

Figure HT1-2. Placement of chassis deck to front panel

4. Attach the rear wheel. This is accomplished by gluing the dowel, passed through the center of the wood bead, to the rear panel.

Figure HT1-3. Adding the rear wheel and axel to chassis

226 | Learn to Program in ArduinoTM C: 18 Lessons, from setup() to robots

5. Turn the robot body over after the glue used to attach the rear wheel is dry and cured. Use the nylon screws to attach the four nylon standoffs to the top of the robot deck.

Figure HT1-4. Chassis with nylon standoffs

Caution

Use only nylon screws to mount the Arduino.™ Metal screws can damage the nylon standoffs and—on some versions of the Arduino™—can cause an electrical short.

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HT6. Attach the Arduino™ Uno to the standoffs, again using the nylon screws.

Figure HT1-5. Arduino™ Uno attached to chassis body with nylon screws

7. Use the metal screws and hex nuts to mount the DC motors to the side panels of the robot body:

Figure HT1-6. DC motor mounted to side panel of robot chassis

228 | Learn to Program in ArduinoTM C: 18 Lessons, from setup() to robots

8. Mount the wheels to the motors by first aligning them with the flat sides of the motor shaft and then pressing the wheels on gently.

HT1-7. Wheels mounted to DC motors

The rolling robot body is now ready to be used. This robot is used in Lessons 15 and 18.